A series of enoyI-ACP reductase (Fabl) inhibitors have been identified with potent, narrow spectrum in vitro antibacterial activity against the agent of Tularemia, Francisella tularensis, as well as excellent in vitro potency against Staphylococci. Lead compounds have shown good in vivo activity in treating Staphylococcus aureus infections in rats and have good oral bioavailability. We propose experiments to assess the in vivo safety of the lead compounds, the frequencies and mechanisms of resistance development, and the efficacy of the lead compounds in animal models of F. tularensis infection. The experiments in this application aim to complete the preclinical characterization of the lead compounds, identify additional compounds with improved characteristics that retain excellent potency against Staphylococci and Francisella, and produce sufficient cGMP material to initiate Phase I clinical studies. We will determine the high-resolution protein structures of the Staphylococcal and Francisella Fabl targets to guide the medicinal chemistry efforts. We aim to select a development candidate compound from this program that has excellent antimicrobial activity both in vitro and in vivo against Staphylococci and Francisella and that can be formulated for both IV and oral administration. Phase I and Phase II clinical trials are proposed in Years 4 and 5, as a narrow spectrum agent for the treatment of Staphylococcal infections. This funding will assure rapid progress of this new class of antibacterial agent through the last stages of discovery and preclinical studies and into the initiation of clinical trials. The funding will also assure that there are sufficient F. tularensis microbiological data and animal model data to warrant inclusion of the information on the product label as a narrow spectrum agent that could be used in the event of a F. tularensis release.